The invention relates to change speed transmissions in general, and more particularly to improvements in transmissions of the type known as continuously variable transmissions (CVT) which can be utilized with advantage in the power trains of motor vehicles, e.g., to transmit torque from the output element of a prime mover (such as the camshaft or the crankshaft of an internal combustion engine) to the front and/or rear wheels of a motor vehicle.
A continuously variable transmission normally comprises a first shaft which can receive torque from a prime mover, a second shaft which is or can be parallel with the first shaft, an adjustable pulley or sheave on each of the two shafts, and an endless flexible element (such as a chain or a belt and hereinafter referred to as chain) trained over the two pulleys to transmit torque from the first shaft to the second shaft when the first shaft is driven by the prime mover. The two pulleys are adjustable and, to this end, each pulley comprises a first conical flange which is affixed to the respective shaft, and a second conical flange which is rotatable with the first flange and is movable axially relative to the respective shaft toward and away from the respective first flange. Such adjustability of the pulleys enables the chain to move one of its looped portions radially inwardly toward one of the shafts while its other looped portion moves radially outwardly and away from the other shaft, or vice versa.
It is already known to make at least one flange of each adjustable pulley of one or more parts at least one of which consists of a metallic sheet material. This contributes to lower cost and to a reduction of the overall weight of the transmission. The axially movable flanges normally cooperate with cylinder and piston units which define with the movable flanges one or more plenum chambers for the reception of a hydraulic fluid which compels the respective mobile flange to move axially toward the associated axially fixed flange. Such movability of the axialy movable flanges is utilized to establish a desired amount of friction between the chain and the adjacent conical surfaces of the flanges (this ensures that the chain shares the angular movements of the flanges or that the chain is entrained with a desired degree of slip) Axial movability of one flange of each pulley is further utilized to select a desired transmission ratio by moving one looped portion of the chain away from the periphery of the respective shaft while the other looped portion of the chain is compelled to move toward the periphery of the associated shaft.
Continuously variable transmissions are often preferred over automatic transmissions which employ a hydrokinetic torque converter in combination with a so-called bypass or lockup clutch. The reason is that a power train employing a continuously variable transmission affords a greater comfort to the occupant or occupants of the motor vehicle because the shifts into different gear ratios invariably take place gradually without any or without appreciable shocks. Moreover, the utilization of a continuously variable transmission in the power train entails substantial savings in fuel requirements of the motor vehicle.
Published German patent application Serial No. 43 42 736 A1 discloses a continuously variable transmission wherein the axially shiftable flange of each adjustable pulley is located between the corresponding axially fixed flange and a support which is affixed to the respective shaft. The support and the adjacent axially movable flange define a plenum chamber which can receive pressurized hydraulic fluid to move the axially movable flange toward the respective fixedly mounted flange. The flanges are or can be made of a metallic sheet material, and this can entail considerable savings in the initial cost of the adjustable pulleys. However, the axially movable flanges and the adjacent fixedly mounted supports are designed to define a single plenum chamber for each of the two pulleys. This is unsatisfactory in those types of continuously variable transmissions wherein each axially shiftable flange must be adjusted by a first unit to select the frictional engagement with the adjacent portion of the chain as well as by a second unit which enables the transmission to select the desired speed ratio, i.e., any one of an infinite number of different speed ratios.
An object of the invention is to provide a novel and improved continuously variable transmission, particularly for use in the power trains of motor vehicles.
Another object of the invention is to provide novel and improved adjusting means for the adjustable flanges of pulleys which can be utilized in continuously variable transmissions.
A further object of the invention is to provide novel and improved fluid-operated adjusting systems for the adjustable flanges of pulleys in continuously variable transmissions.
An additional object of the invention is to provide novel and improved adjustable pulleys for use in continuously variable transmissions.
Still another object of the invention is to provide a power train which is designed for use in motor vehicles and embodies a continuously variable transmission of the above outlined character.
A further object of the invention is to provide a transmission which constitutes an improvement over and a further development of continuously variable transmissions of the type disclosed in published German patent application Serial No. 43 42 736 A1.
Another object of the invention is to provide a simple, compact and inexpensive continuously variable transmission which can be utilized as a superior substitute for heretofore known transmissions of such character in the power trains of motor vehicles.
An additional object of the invention is to provide novel and improved combinations of axially movable conical flanges and moving means therefor for use in power trains employing continuously variable transmissions.
One feature of the present invention resides in the provision of a transmission, such as a continuously variable transmission, which comprises a shaft rotatable about a predetermined axis, and a pulley having a first flange affixed to the shaft and a second flange rotatable with and movable axially of the shaft toward and away from the first flange. The flanges have confronting conical surfaces which surround an annular space having a width, as seen in the axial direction of the shaft, which varies in response to movement of the second flange relative to the first flange. At least one of the flanges comprises a plurality of interconnected components consisting at least in part of a metallic sheet material. The transmission further comprises an endless flexible element which is trained over the pulley and includes a looped portion received in the aforementioned annular space, and means for moving the second flange. The moving means includes a support which is affixed to the second flange and the latter is disposed between the support and the first flange. The support and the second flange define a plurality of annular plenum chambers, and the moving means further comprises means for sealing the chambers; such sealing means extends in at least one of a plurality of directions including radially and axially of the shaft.
The at least one flange is or can constitute the axially movable second flange; such second flange has a side which confronts the support and is or can be defined by at least one of the components which consist of or contain sheet metal. The at least one component can comprise a conical disc and the support can comprise a supporting part non-rotatably mounted on the shaft, a frustoconical part connected with a median portion of the at least one component and extending from the at least one component axially end radially of the shaft toward the periphery of the shaft, and a second component remote from the axis of the shaft and defining with the frustoconical part one of the plenum chambers.
In accordance with a presently preferred embodiment, the second flange comprises a frustoconical component which is adjacent the annular space, and the support is non-rotatably mounted on the shaft and includes a frustoconical first portion extending from the median portion of the frustoconical component toward the periphery of the shaft, a second portion which is at least substantially parallel to the axis of the shaft and extends from the frustoconical component away from the annular space, and a third portion which extends from the second portion radially outwardly and away from the shaft. One of the plenum chambers surrounds the second portion of the support and another chamber is located radially inwardly or outwardly of the one chamber.
In accordance with another presently preferred embodiment, the at least one flange is the second flange and the second flange comprises a frustoconical component adjacent the annular space. The support comprises a frustoconical first portion extending from a median portion of the frustoconical component toward the periphery of the shaft, a second portion which extends in substantial parallelism with the axis of the shaft and away from the annular space, and a third portion which is bent radially outwardly from the second portion. One of the chambers is defined, at least in part, by the first and second portions of the support, and another chamber is defined by the second and third portions of the support.
The support can consist of a single piece of sheet metal; alternatively, the support can be assembled of a plurality of parts each of which is made or at least some of which are made of sheet metal.
If the support for at least one of the flanges includes first, second and third portions which consist of a metallic sheet material and are disposed at different radial distances from the axis of the shaft, the second and third portions of the support can be made of one piece separately from the third portion of the support.
The second flange can comprise a frustoconical component having a substantially circular radially inner portion which surrounds; and is movable axially of the shaft. Alternatively, the radially inner portion of the frustoconical component of the second flange can have a polygonal profile surrounding and being movable axially of a complementary polygonal profile on the shaft.
At least one of the flanges can include a radially inner portion having a cylindrical internal surface which surrounds a complementary external surface on the shaft. The inner portion merges into a substantially frustoconical component forming part of the respective flange.
At least one of the flanges can comprise a frustoconical component which is adjacent the annular space and at least one substantially frustoconical stabilizing portion for the frustoconical component.
The first flange can comprise a frustoconical component which is adjacent the annular space, and a supporting device for the frustoconical component. The shaft for such first flange can have a first substantially annular shoulder which abuts a portion of the frustoconical component and a second substantially annular shoulder abutting a portion of the supporting device.
At least one of the flanges can comprise a frustoconical component adjacent the annular space and a body of foam which is adjacent and attached to a surface of the frustoconical component facing away from the annular space.
The first flange can include a portion which is remote from the shaft, and a gear which is provided on such remote portion of the first flange.
The second flange can include a frustoconical component which is adjacent the annular space, and a member which consists, at least in part, of sheet metal and forms part of a torque sensor. The member is adjacent a side of the frustoconical component which faces away from the annular space.
It is also possible to design the transmission in such a way that the first flange includes a frustoconical component adjacent the annular space, and a member consisting at least in part of sheet metal and forming part of a torque sensor. The member is adjacent a side of the frustoconical component which faces away from the annular space.
Another feature of the invention resides in the provision of a transmission, such as a continuously variable transmission, which comprises a shaft rotatable about a predetermined axis, and a pulley having a first flange affixed to the shaft and a second flange which is compelled to rotate with and is movable axially of the shaft toward and away from the first flange. In accordance with a feature of the instant invention, at least one of the flanges comprises a plurality of interconnected components (or groups of two or more one-piece components each) consisting at least in part of sheet metal. Such transmission further comprises an endless flexible torque transmitting element (such as an endless chain or an endless belt) having a portion which is trained over the pulley and is disposed between the two flanges.
It is possible to assemble each of the two pulleys of two or more components at least one of which is made of sheet metal, e.g., in a stamping, upsetting, cutting, embossing or other suitable machine.
The construction of one of the two flanges can differ from that of the other flange.
The improved transmission can further comprise a torque sensor, and at least one of the flanges can include at least one portion which forms part of the torque sensor. This torque sensor can receive torque from a suitable prime mover, such as the combustion engine of a motor vehicle, and can define two plenum chambers which ar connectable with or sealable from each other.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improve transmission itself, however, both as to its construction and the modes of assembling and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.